Tetrazaindene stabilizer for photographic emulsions sensitized with alkylene oxide polymers



United States PatentO 16 Claims, cl. 95-7 This invention relates to foginhibiting agents and stabilizers for-photographic emulsions and tophotographic emulsions containing them.

It is well known that photographic emulsions on storagetend to losesensitivity and to become spontaneously developablev without exposure tolight. There is normally a. detectable amount of. the silver saltreduced during I development inthe areas where no exposure was given;this is. commonly called fog, and sometimes called chemical fog where itis necessary to distinguish be-. tween it and the effects of accidentalexposure to radiation; in this invention, we are not concerned with thelatter.

Fog depends both onthe emulsion and the conditions (if-development; fora given emulsion it increases with the degree of development. Withconstant development conditions, it tends to increase with time,temperature and relative humidity of storage conditions; it is commonpractice to make accelerated tests of the stability of'vphotographicemulsions by storage at increased tern pe'r'ature or humidity, or both.It is, of course, desirable to have emulsions as stable as possibleunder the condi- I tions of high temperature and humidity which mayoccur in tropical climates, for example. Fog usually appears overthewholearea of the sensitive coating, but when severe, it frequently isnon-uniform. Fog may also be caused by exposure to chemicals, forexample, hydrogen-sulfide and other reactive sulfur compounds, hydro:

gen peroxide vapor, and strongly reducing materials; While antif oggantsand stabilizers may protect; to some extent, against such'eife'cts', itis normally understood that an antifo'ggant protects against spontaneousgrowth of fog during prolonged storage or storage at high temperaturesand'humiditie's, or during development to maximum contrast and speed, orboth. v V

- It is known that the effective sensitivity of photograph:

ic silver halide emulsions may be increa'sedbyadding' to themderivatives of alkylene oxides, such as ethylene oxide-polymershavingmolecular weights of 300'ormo re.

Thelpractical value of these compounds-issevere'ly limited by theirtendency to increase fog on storage of thephotographiofilm; especiallystorage atelevated-temperatures- It has been found difiicultto controland humidities. V this bythe antifoggants commonly available withoutusing quantities. of antifo'ggant' which partly neutralize the speedincreaseobtained from the alkylene oxide derivative'sk It is} therefore,anobject of the present invention to' pr'ovide amethod for stabilizingphotographic emulsions sensitized: with alkyle'ne' oxide derivatives,such as ethylene oxides. A further object is to provide a meansfor-reducing thefogproduced upon keeping of emulsioiisso sensitized,especially emulsions stored under A still further object is to provide ameans for stabilizing thespeed and contrastiof emulsions sosensitized.Other objects wnrappear from the following description ofmy inven-i'eon.-

tropical or other adverse conditions.

2,756,147 Patented July 24, 1956 ICC? These objects are accomplished, ingeneral, by adding to the emulsion sensitized with alkylene oxidepolymers, S-carboxy 4 hydroxy 1,3,3a,7-tetrazaindene as a stabilizingand fog inhibiting agent.

The alkylene oxide polymers used to sensitize the emulsions may be ofvarious types. The alkylene oxides from which the polymers are derivedcontain from 2 to 4 carbon atoms, e. g., ethylene oxide, propylene oxideand butylene oxide. The preparation of polymers from these compounds isdescribed in Ellis, The Chemistry of Synthetic Resins (1935.), pages 990to 994. These compounds are also referred to as polyalkylene glycols andtheir use as sensitizers for silverhalide emulsions is described in U.S. Patents 2,423,549 and 2,441,389.

Various derivatives of alkylene oxides can also be used to sensitizethesilver halide emulsions, e. g. condensation products of alkylene oxidewith glycols, such as those having from to, 18 carbon atoms, asdescribed in U. S. Patent 2,240,472 and British Patent 443,559, as wellas condensationproducts of alkylene oxides with aliphatic alcohols,aliphatic acids and aliphatic amines, and with phenols, that is,polyalkylene ethers, esters and amineethers', the preparation of whichis described in U. S. Patent 1,970,573, and condensation products of"alkylenc oxidesvfitli hexitol ring dehydration products, as described inU. S; Patent 2,400,532. I I

In eats-n e the polyalkyle'ne oxide or derivative of alkylen'el oxideshould have a molecular weightgof, at least 300 and preferably amolecular weight of 1500 to 40.00, or more. v v

The principal purpose of our invention is to provide a means. formaintaining the sensitivity and fog of silver halide emulsions at orclose to initial optimum values under conditions of high temperature orhumidity or both; Preferably the fog inhibitors which we proposetouseare added to the emulsion at any stage during the process ofmanufacture prior to coating the emulsion. The tetrazaindene foginhibitor can be added to the emulsion in solution in any convenientsolvent not injurio'us' to the emulsion, such as lower alcohols orketones.

A solution of the tetrazaindene which we employ when added in suitableconcentration beforev coating to unsensitized or optically sensitizedsilver halide emulsions usually does not appreciably affect thesensitivity and fog when measurements are made soon after coating.However, when sensitometric measurements are made after appreciableintervals of time under tropical or dry condijtions of storage atelevated temperatures, this compound does. stabilize, speed and maintainfog at a low level.

The alkylene oxide derivatives used to sensitize the emulsions can beillustrated by the following specific examples, although our inventionis in no way limitedto the use of these specific compounds.

HOCHzCHzO(CHzCHzO)}.OHCHiOHi Polyethylene oxideDi-(polyethylene-glycoxy)-decane HOOHzOHgO(CHzCHtOhC'HzCHiOCnHi:Polyethylene oxide oleyl ether where n an integer greater than about 10The preparation of silver halide emulsions involves three; separateoperations: 1) the emulsification' and digestion or ripening of thesilver halide, (2) the freeing' of the emulsion from aqueous solublesalts usually by washing,- (3) the" second digestion or after-ripening"to' obtain increased sensitivity-(Mees, The Theory of the PhotographicProcess, 1942, page 3). Thefog inhibiting 3 agent can be added at anystage, preferably after the final digestion.

The photographic emulsions which we use are of the developing-out typeand best results have been obtained with gelatino-silverbromoiodicleemulsions. However, emulsions of varying halide content canbe used.

The emulsions can be chemically sensitized by any of the acceptedprocedures, in addition to or in combination with the sensitizing withalkylene oxide polymers. The emulsions can be digested with naturallyactive gelatin, or sulfur compounds can be added, such as thosedescribed in Sheppard U. S. Patent 1,574,944 and U. S. 1,623,499, andSheppard and BrighamU. S. Patent 2,410,689.

The emulsions can also be treated with salts of the noble metals, suchas ruthenium, rhodium, palladium, iridium and platinum, all of whichbelong to group ,VIII of the periodic table of elements and have anatomic weight greater than 100. Representative compounds are ammoniumchloropalladate, potassium chloroplatinate and sodium chloropalladite,which are used for sensitizing in amounts below that which produces anysubstantial fog inhibition, as described in Smith and Trivelli U. S.Patent 2,448,060, and as antifoggants in higher amounts, as described inTrivelli and Smith U. S. Patents 2,566,245 and 2,566,263.

The emulsions can also be chemically sensitized with gold salts asdescribed in Waller and Dodd U. S. Patent 2,399,083, or stabilized withgold salts as described in Damschroder U. S. Patent 2,597,856 and Yutzyand Leermakers U. S. Patent 2,597,915-: Suitable compounds are potassiumchloroaurite, potassium aurithiocyanate, potassium chloroaurate, aurictrichloride and Z-aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agents,such as stannous salts (Carroll U. S. Patent 2,487,850), polyamines suchas diethylene triamine (Lowe and Jones U. S. Patent 2,518,698),polyamines such as spermine (Lowe and Allen U. S. Patent 2,521,925), orbis-(p-aminoethyl) sulfide and its watersoluble salts (Lowe and Jones U.S. Patent 2,521,926).

The emulsions can also be stabilized with the mercury compounds ofAllen, Byers and Murray U. S. application Serial No. 319,611, now U. S.Patent No. 2,728,663, Carroll and Murray U. S. application Serial No.319,612, now U. S. Patent No. 2,728,664, and Leubner and Murray U. S.application Serial No. 319,613, now U. S. Patent No. 2,728,665, allfiled November 8, 1952.

The sensitizing and stabilizing combinations of poly-, alkylene oxidesand tetrazaindene are effective in the presence or absence of opticalsensitizing dyes. Since optical sensitizing may affect stability ofemulsions with respect to sensitivity, fog and latent image changes, theaction of the compounds of this invention is not completely independentof optical sensitizing or other emu1 sion variables. We have found,however, that both unsensitized emulsions and emulsions sensitized withcyanine or merocyanine dyes or both can be treated with polyalkyleneoxides and tertrazaindene according to our invention.

The most useful concentration of the tetrazaindene compound in theemulsion is from about 0.01 gram to 4 grams per gram mole of silverhalide in the emulsion. Although higher amounts can be used, no emulsionis likely to tolerate as much as 5 times this upper limit withoutserious desensitization. Optimum concentrations are about 0.2 to 1.0gram of the tetrazaindene per gram mole of silver halide. These amountscan be used in combination with one or more of the chemical sensitizingand stabilizing agents listed above.

The stabilizing action was determined by incubation of the emulsions forone week at 120 F. and constant,

humidity unless otherwise stated in the examples. The

results of aging tests are tabulated below and compare.

speed, gamma and fog of the emulsions with and without the stabilizingcompound.

Example 1 One liter of a high speed gelatino-silver bromiodide emuslionwas digested with a sulfur compound, such as disclosed in Sheppard U. S.Patent 1,574,944, andpotassium chloroaurate, and panchromaticallysensitized with an optical sensitizing dye. To a portion of the emulsionwas added 0.9 gram per gram mole of silver halide of5-carboxy-4-hydroxy-1,3,3a,7-tetrazaindene and to another portion of thesame emulsion was added 0.75 gram per gram mole of silver halide of thecondensation product of oleyl alcohol with approximately 15 moles ofethylene oxide. To a third portion of the emulsion were added 0.9 gramper gram mole of silver halide of 5-carboxy-4-hydroxy-1,3,3a,7-tetrazaindene and 0.75 gram per gram mole ofsilver halide of the condensation product of oleyl alcohol withapproximately 15 moles of ethylene oxide.

The emulsions were coated on cellulose acetate film base and wereexposed for 5 second on an Eastman IB sensitometer and processed for 4minutes in a developer of the following formula:

. Grams N-methyl-p-aminophenol sulfate 2.5 Hydroquinone 2.5 Sodiumsulfite (desiccated) 30 Sodium metaborate Q. 10 Potassium bromide 0.5

Water to 1 liter.

A fourth emulsion coating containing 0.75 gram per gram mole of silverhalide of the oleyl alcohol-ethylene oxide condensation product and 3.0grams per gram mole of silver halide of the tetrazaindene was prepared,ex posed and processed as before. The films with and without the addendawere held at F. and constant humidity for 1 week and were then exposedand developed as before. The results of tests for speed (IO/i), gammaand fog, before and after incubation of each of the samples were asfollows:

In a manner similar to that, illustrated in the above table, otherethylene oxide polymers can be employed to advantage in our invention.For example, in place of the oleyl alcohol-ethylene oxide condensationproduct employed above, condensation products of ethylene oxide withlauric acid (1 mole of lauric acid to approximately 26 moles of ethyleneoxide), phenol (1 mole of phenol to approximately 28.3 moles of ethyleneoxide), glycine, laurarnide, glucose monolaurate, etc. can be used. Suchcondensation products can be prepared as described in Carroll U. S.application Serial No. 426,543, filed April 29, 1954, now U. S. Patent2,743,180, issued April 24, 1956.

The polyethylene oxide polymers used in the emulsions according to ourinvention can beprepared either by polymerizing ethylene oxide in thepresence of aliphatic acids, aliphatic amines or phen0ls, or by reactingthe polymerized polyethylene oxide with aliphatic acids, acid chlorides,or esters, which produces similar products.

Instead of incorporation in the silver halide emulsion;

thetetrazaindeneof our invention can-be ingorpqrated ina. colloid layer,such as agelatin layer ncontact. ital; theemulsion.. p

. The tetrazaindene whichv we have described can be used in variouskinds of photographic emulsions. In additionto being useful innon-sensitized em 1 'ons, it can also be used in orthochrornatic,panchromatic and X-ray emulsions. If used with sensitizing, dyes, it canbe added to the emulsion before or after the dyes are added. Varioussilver salts can be, used as the sensitive salt, such as silver bromide,silver iodide, silver chloride, or mixed silver halides. Thetetrazaindene and alkylene oxide polymers can be used in emulsionsintended for color photography, for example, emulsions containingcolor-forming couplers, or emulsions to be I developed by solutionscontaining couplers.

The dispersing agents can be gelatin or other colloid, such ascollodion, albumen, cellulose derivatives or synthetic resins.

The 5-carboxy-4-hydroxy-1,3,3a,7-tetrazaindene used as a fog inhibitingor stabilizing agent in our invention can be prepared as follows:

Example A .5 -carbethxy-4-hydr0xy-1 ,3,3a,7-tetrazaindene ExampleB.-carboxy-4-hydr0xy-1,3,3a,7-tetrazaindene HaCzO O C A mixture of 1 g.of S-carbethox -4-hydroxy-1,3,3a,7- tetrazaindene and ml. of 1 Nhydrochloric acid were refluxed for five hours. The solid dissolved onheating to reflux, but after about one to two hours a solid began toseparate from the solution. After cooling, the solid was collected andrecrystallized from water to give 0.5

g. of 5-carboxy-4-hydroxy-1,3,3a,7-tetrazaindene (M. P.

Analysis.Calcd. for Cs-H4N4O3: C, 40.0; H, 2.2; N, 31.1. Found: C, 39.4;H, 2.4; N, 31.0.

What we claim as our invention and desire secured by Letters Patent ofthe United States is:

1. A photographic silver halide emulsion sensitized with an alkyleneoxide polymer selected from the class consisting of (1) polyalkyleneglycols, (2) condensation products of an alkylene oxide with a glycol,(3) condensation products of an alkylene oxide with an aliphaticcompound selected from the group consisting of monohydric alcohols,acids and amines, (4) condensation prod nets of an alkylene oxide with aphenol, and (5) condensation products of an alkylene oxide with hexitolring dehydration products, said alkylene oxide containing from 2 to 4carbon atoms and said alkylene oxide polymer having a molecular weightof at least 300, said photographic silver halide emulsion containing5-carboxy-4- hydroxy-l,3,3a,7tetrazaindene as a fog inhibiting agent.

2. A photographic silver halide emulsion as defined in @laim 1 where n.sa d al ylene oxide. p ly erisan yleneoxidepely ier.

3. A photographic silver bromiodide emulsiodsensh tized with an ethyleneoxide polymer selected from the group consisting of 1) polyethyleneglycols, (2) com densation products of ethylene oxide with glycols,;(3.) condensation products of ethylene oxide with aliphatic compoundsselected from the group consisting of'mono-z hydric alcohols, acids andamines, (4) condensation prod: nets of ethylene oxide. with a phenol,and (5) conderisa: tion products of ethylene oxide with hexitol ringdehydration products, said ethylene oxide polymer having a molecularweight of at least 300, said photographic'silver bromiodide emulsioncontaining 5-carboxy-4-hydroxy- 1,3,3a,7-tetrazaindene as a foginhibiting agent.

4. A photographic silver halide emulsion sensitized with an ethyleneoxide polymer having a molecular weight of at least 300, and containing5-carboxy-4- hydroxy-1,3,3a,7-tetrazaindene as a fog inhibiting agent.

5. A photographic silver halide emulsion sensitized with a condensationproduct of ethylene oxide and an aliphatic monohydric alcohol, saidcondensation product having a molecular weight of at least 300, andcontaining 5-carboxy-4-hydroxy-1,3,3a,7-tetrazaindene as a foginhibiting agent.

6. A photographic sulfur-sensitized silver halide emulsion additionallysensitized with an alkylene oxide polymer selected from the classconsisting of (1) polyalkylene glycols, (2) condensation products of analkylene oxide with a glycol, (3) condensation products of an alkyleneoxide with an aliphatic compound selected from the group consisting ofmonohydric alcohols, acids and amines, (4) condensation products of analkylene oxide with a phenol, and (5) condensation products of analkylene oxide with hexitol ring dehydration products, said alkyleneoxide containing from 2 to 4 carbon atoms and said alkylene oxidepolymer having a molecular weight of at least 300, said photographicsilver halide emulsion containing5-carboxy-4-hydroxy-1,3,3a,7-tetrazaindene as a fog inhibiting agent.

7. A photographic silver halide emulsion as defined in claim 6 whereinsaid alkylene oxide polymer is an ethylene oxide polymer.

8. A photographic sulfur-sensitized silver bromiodide emulsionadditionally sensitized with an ethylene oxide polymer selected from thegroup consisting of (1) polyethylene glycols, (2) condensation productsof ethylene oxide with glycols, (3) condensation products of ethyleneoxide with aliphatic compounds selected from the group consisting ofmonohydric alcohols, acids and amines, (4) condensation products ofethylene oxide with a phenol, and (5) condensation products of ethyleneoxide with hexitol ring dehydration products, said ethylene oxidepolymer having a molecular weight of at least 300, said photographicsilver bromiodide emulsion containing5-carboxy-4-hydroxy-l,3,3a,7-tetrazaindene as a fog inhibiting agent.

9. A photographic sulfur-sensitized silver halide emulsion additionallysensitized with an ethylene oxide polymer having a molecular weight ofat least 300, and containing 5-carboxy-4-hydroxy-1,3,3a,7tetrazaindeneas a fog inhibiting agent.

10. A photographic sulfur-sensitized silver halide emulsion additionallysensitized with a condensation product of ethylene oxide and analiphatic monohydric alcohol, said condensation product having amolecular weight of at least 300, and containing5-carboxy-4-hydroxy-l,3, 3a,7-tetrazaindene as a fog inhibiting agent.

11. The emulsion of claim 6 which is additionally chemically sensitizedwith gold salts.

12. The emulsion of claim 9 which is additionally chemically sensitizedwith gold salts.

13. The emulsion of claim 9 which is additionally stabilized withmercury salts.

14. The emulsion of claim 9 which is additionally 7 chemicallysensitized with gold salts and stabilized with a salt of the generalformula selected from the group consisting of R2MX5,R2M,X4 and R3M"Xs,where R is selected from the group consisting of hydrogen, an alkalimetal and ammonium, M is a metal selected from the group consisting ofplatinum, palladium, iridium, rhodium and ruthenium, M is a metalselected from the,

group consisting of platinum and palladium, and M' is a metal selectedfrom the group consisting of iridium and rhodium, and X is a halogenatom.

15. The emulsion of claim 9 which is, additionally chemically sensitizedwith gold salts and stabilized with a palladium salt having thestructure RzPdCls where R is selected from the group consisting ofalkali metal and ammonium.

16. The emulsion of claim 9 which is additionally chemically sensitizedwith gold salts and stabilized with mercury salts.

No references cited.

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION SENSITIZED WITH AN ALKYLENEOXIDE POLYMER SELECTED FROM THE CLASS CONSISTING OF (1) POLYALKYLENEGLYCOLS, (2) CONDENSATION PRODUCTS OF AN ALKYLENE OXIDE WITH A GLYCOL,(3) CONDENSATION PRODUCTS OF AN ALKYLENE OXIDE WITH AN ALIPHATICCOMPOUND SELECTED FROM THE GROUP CONSISTING OF MONOHYDRIC ALCOHOLS,ACIDS AND AMINES, (4) CONDENSATION PRODUCTS OF AN ALKYLENE OXIDE WITH APHENOL, AND (5) CONDENSATION PRODUCTS OF AN ALKYLENE OXIDE WITH HEXITOLING DEHYDRATION PRODUCTS, SAID ALKYLENE OXIDE POLYFROM 2 TO 4 CARBONATOMSAND SAID ALKYLENE OXIDE POLYMER HAVING A MOLECULAR WEIGHT OF ATLEAST 300, SAID PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING5-CARBOXY-4HYDROXY-1,3,3A,7-TETRAZAINDENE AS A FOG INHIBITING AGENT.